A deadly chill has much of the United States and Canada in its wintry grip, as a record-breaking cold snap brought temperatures lower than on the surface of Mars.

All of Canada and all the US states bar tropical Hawaii recorded temperatures below freezing yesterday, even usually sunny and warm Florida and California.

But the most dangerous cold hit the Midwest states, where a record low temperature of -38C was recorded in the town of Embarrass in Minnesota.

NASA's Mars Rover Curiosity has been sending back daily temperature readings from its tour of Mars ranging from -25C to -31C.

At least eight deaths have been reported across the country because of the polar air mass sweeping south during the past few days.

Authorities have put about half of the US under a wind chill warning or cold weather advisory.

Major US cities are in the grip of temperatures well below freezing, with Chicago seeing -17C, Detroit -18C, Pittsburgh -15C, Washington DC -7C and Boston -9C.

New York's Central Park recorded the lowest temperature for the date, -16C, rising to -13C yesterday afternoon with wind chills making it feel much colder, meteorologists said.

Schools in Minneapolis and Chicago were closed. Cleveland remained below freezing after temperatures fell to -24C on Monday, breaking a 130-year-old record.

In the normally mild south, Atlanta recorded its coldest weather on the date in 44 years, when the temperature dropped to -14C.

Temperatures in northern Florida also briefly dropped below freezing, though the state's citrus crop was unharmed, according to a major growers' group.